1. Field of the Invention
The present invention relates to the acquisition of several distinct quantities with a view to their exploitation by a user system. It concerns, more particularly, but not exclusively, the acquisition of analogue quantities with a view to their exploitation by a digital processing system.
2. Discussion of the Background
In order to operate, numerous electronic systems for digital processing require periodic acquisitions of several distinct analogue quantities of diverse origins. These acquisitions are usually effected by means of a sampling analogue/digital converter equipped at the input with an analogue multiplexer with multiple inputs. The analogue multiplexer is addressed monotonically, by way of one or more chained counters which count at the sampling and conversion rate of the analogue/digital converter so as to have all of its inputs scanned periodically.
When the number of analogue quantities to be taken into account by the user system is sizeable, the analogue multiplexer has a staged architecture so as to reduce the number of switches necessary to service all its inputs. In order to cater for periodic scanning of the inputs of an analogue multiplexer with staged architecture, it is customary to address each stage of switches of the multiplexer by means of an elementary counter, to place the various elementary counters in series and to increment them by applying, at a regular rate, pulses to the counting input of the elementary counter of lowest weight, the elementary counters of higher weights being incremented by means of the overflow pulses of the counters of immediately lower weight.
This poses a problem insofar as the staged architecture of an analogue multiplexer is rarely used in a complete manner, this use depending on the context, that is to say on the number of analogue quantities whose exploitation is actually necessary to the relevant user system. Thus, fairly frequently a certain number of inputs of a multiplexer with staged architecture are not used, these inputs possibly not being hard-wired and the switches assigned solely to these unused inputs possibly themselves being absent.
Use of the customary method of addressing leads to systematic scanning of all the inputs of the multiplexer which are rendered possible by the staged architecture, whether or not these inputs are used and whether or not they are hard-wired. This results in needless data acquisition operations which slow down the consideration of the useful data and needlessly load the operating system.